1. Field of Invention
The invention relates to a system for opening and closing a vacuum chamber for the purpose of thermoforming and/or evacuating, modifying atmosphere and sealing packages for both food and non-food stuffs, insuring that both upper and lower vacuum chambers are kept in alignment at all times.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
The prior art includes numerous machines and methods for filling and sealing packages employing heat sealing platens. These prior art methods and machines generally employ guide posts that are part of the frame of the machine so that closing forces on filled and sealed packages are a function to the overall machine rather than a function of the filling or sealing platens themselves. Further in such prior art the duration of the sealing forces and the heating of the heat seal are the same since sealing and heating are not separately controlled.
In the prior art clamping forces as high as 40,000 pounds are transmitted to and through the frame causing flexing, warping and fatigue in the frame which results in loss of tolerance in the clamping portion of the platen machine. Relevant prior art includes Janovtchik U.S. Pat. No. 4,148,933 and Ito U.S. Pat. No. 5,176,923. In Ito U.S. Pat. No. 5,176,923 (FIG. 1), a pair of guideposts 5, which are part of the machine frame raise or lower upper mold 2 or lower mold 3.
In contrast to such prior art the invention provides a filling and sealing machine that does not provide filling or sealing as a function of the overall machine but instead as a function of the platens themselves which are disposed on alignment shafts separate from the machine frame. The novel combination of platens, shaft and support provides a greater, more controlled and precise mating of top and bottom platens to assure closer tolerances that do not depend on the support frame of the machine to maintain those tolerances. Further in accordance with the invention the heating element is independently activated to provide control over the duration of the heat sealing portion of the operation. The sealing and filling tolerances achieved by the novel combination also provides greater control over forces since the forces are a function of the novel combination rather than of the entire machine.
Other prior art platen machines employ an upper platen, a lower platen and a moveable platen disposed between the upper and lower platen. Representative of this prior art includes Tanaka, et al. U.S. Pat. No. 4,904,173 for use in plastic molding arts which employs an upper platen 10, a lower platen 11 and a moveable platen 13 with a tie bar 12. In Tanaka, et al. U.S. Pat. No. 4,904,173 like the other prior art, the upper and lower platens are carried by the frame of the machine so that the closing forces and the precision of the machine is a function of the overall machine rather than as a function of the operation of the platens themselves. The invention in contrast provides for the precision of the closing forces operating as a function of the movement of the platens themselves by employing a common alignment shaft between the upper and lower platens. This arrangement on the common alignment shaft allows the upper and lower platens to move toward each other with great precision. A carrier plate assembly is mounted to a support frame, which frame merely provides support for the novel packaging machine without interfering with the filling and sealing operations of the novel packaging machine.